1. Field of the Invention
This invention relates to equipment for drilling operations.
2. Description of the Prior Art
In conventional drilling operations, mud or other drilling fluid is pumped down a hollow bore in the drill string and is ejected from the drill bit to lift the drill cuttings out of the bore-hole.
In an inclined well-bore it is been found that at a certain deviation or sail angle, some of the drill cuttings being transported back to the surface by the drilling fluid fall out of the main flow and settle on the lower portion of the bore-hole. These cuttings interfere with the drilling process and especially with the rotation of the rotating drill-pipe which also lies on the low side of the bore-hole.
The flow of returning drilling fluid which carries the cuttings is not uniform across the diameter of the bore-hole. On the low side of the bore-hole the flow is at a minimum and the capacity of the drilling fluid to transport drilling cuttings and solid particles is reduced.
To overcome this problem it is known to fit one or more cutting bed impellers to the drill-pipe. The impellers are integrally formed with a length of drill-pipe and comprise a body portion having a central longitudinal bore and a plurality of paddles in the form of single spiral blades which project radially outwardly from the body portion. These types of blade are similar in profile to those used on down-hole drilling stabilizers.
As the cutting bed impeller rotates with the drill-pipe, it disturbs and agitates the settled cuttings and other particles and moves them upwards into the path of the main flow of cutting fluid on the upper side of the bore-hole. Although these tools have proved reasonably effective they have been found to create extra down-hole torque.